(a) Field of the Invention
The present invention relates to a method and apparatus for transmitting/receiving multiple codewords in an SC-FDMA (single carrier frequency division multiple access) system. More particularly, the present invention relates to a method and apparatus for transmitting/receiving data using multiple codewords in a communication system using SC-FDMA.
This work was supported by the IT R&D program of MIC/IITA [2006-S-001-01, Development of Adaptive Radio Access and Transmission Technologies for 4th Generation Mobile Communications].
(b) Description of the Related Art
An OFDMA (orthogonal frequency division multiple access) system divides subcarriers for multiple users, and is suitable to transmit/receive data at a high speed through wire and wireless radio channels. Since the OFDMA system uses a plurality of carriers having orthogonality therebetween, efficiency in the usage of frequency is improved, and processes of modulating/detecting a plurality of carriers in a transmitter and a receiver obtain the same results as IDFT (inverse discrete Fourier transform) and DFT (discrete Fourier transform) are performed on the carriers. Therefore, the OFDMA system can perform the modulating/detecting processes at a high speed using IFFT (inverse fast Fourier transform) and FFT (fast Fourier transform).
Since the OFDMA system is suitable for high-speed data transmission and reception, it has been adopted as a standard scheme of an IEEE 802.11a standard, a high-speed wireless LAN (local area network) of a HIPERLAN/2 system, a broadband wireless access (BWA) system of an IEEE 802.16 standard, a digital audio broadcasting (DAB) system, a digital terrestrial television broadcasting (DTTB) system, an ADSL (asymmetric digital subscriber line), or a VDSL (very high data-rate digital subscriber line).
However, the OFDMA system has a problem in that a PAPR (peak to average power ratio) is high. In order to solve this problem, an SC-FDMA (single carrier frequency division multiple access) system that extends an SC-FDE (single carrier with frequency domain equalization) system to a subcarrier division system has been proposed.
In order to obtain a single carrier characteristic while maintaining frequency orthogonality, the SC-FDMA system is constructed by adding a DFT-spreading structure to the existing OFDMA system.
The SC-FDMA system enables multiple access using frequency domain orthogonality, which is an advantage of the existing OFDMA system, and can reduce a PAPR, which has not been achieved by the existing OFDMA system. However, the SC-FDMA has a problem in that interference between transmission symbols occurs in a frequency selective fading environment, resulting in low performance.
As described above, since the SC-FDMA system transmits or receives only one stream, there is a limitation in removing the interference between the symbols. As a result, the performance of the SC-FDMA system is lowered due to the interference between the symbols in the frequency selective fading environment.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.